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b2c1a77bb3
Only the low bytes are compared. Originally, signed 16-bit compares were optimized into signed 8-bit compares. But, the sign bits are in the high bytes; and, they're equal. Therefore, the low bytes always must be compared as unsigned numbers. Fixes #1348.
55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
/* bug #1348, wrongly optimized integer promotion in comparison */
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#include <stdio.h>
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static const int notrandtab[] = {
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0xffff, 0x7fff, 0x3fff, 0x1fff,
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0x0fff, 0x07ff, 0x03ff, 0x01ff,
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0x00ff, 0x007f, 0x003f, 0x001f,
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0x000f, 0x0007, 0x0003, 0x0001
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};
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static unsigned char notrandcount = 0;
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static int notrand(void)
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{
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return notrandtab[notrandcount & 0x0f];
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}
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static unsigned char n1, n2;
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static unsigned char i, ii, s;
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static unsigned char err = 0;
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static const unsigned char cmptab[] = {
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0xff, 0x7f, 0x3f, 0x1f,
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0x0f, 0x07, 0x03, 0x01,
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0x80, 0x40, 0x20, 0x10,
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0x08, 0x04, 0x02, 0x01
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};
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int main(void)
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{
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for (ii = 0; ii < 16; ++ii) {
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s = cmptab[ii];
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for (i = 0; i < 16; ++i) {
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n1 = n2 = 0;
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if ((notrand() & 0xff) > s) {
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n1 = 1;
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}
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if ((notrand() & 0xffu) > s) {
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n2 = 1;
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}
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printf("%5d > %3d %u(%02x) %u(%02x) %s\n",
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notrandtab[i], s,
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n1, (notrand() & 0xff),
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n2, (notrand() & 0xffu),
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n1 == n2 ? "=" : "!=");
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if (n1 != n2) {
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err = 1;
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}
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notrandcount++;
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}
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}
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return err;
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}
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